The invention relates generally to vacuum cleaners, and more particularly to compact bagless vacuum cleaners including a cylindrical cyclonic separation/dirt collection container with a central tube and openable bottom to enhance separation of dirt from the air stream and retention of dirt particles within a lower section of the container.
Cyclonic vacuum cleaners have been known for some time. For example, European Patent No. EP 0 042 723 and U.S. Pat. No. 4,593,429 to James Dyson discloses a vacuum suction cleaning device including two cyclone units in series operating successively to extract dirt particles from an air flow. One of the two cyclones has a substantially frusto-conical shape serving to increase the velocity of the dirt particles so that the cyclone is capable of depositing the fine dust particles in a small diameter collection chamber relative to the diameter of the cone opening. Prior to the air entering the cyclone, dirty air enters tangentially against the wall of a cylindrical outer chamber operating as a cyclone to remove coarse dirt particles from the dirty air entering the device.
In addition to devices wherein the successive cyclones are coaxial as in the above noted publications, Dyson in U.S. Pat. No. 4,373,288 places frusto-conical cyclones side by side. In this configuration, the device is designed to remove dirt through the two cyclones operating in series. The principal objective in all these devices is to avoid the need to utilize a bag as in conventional vacuum cleaners. In these conventional devices, air is drawn through the appliance by a fan that creates a large pressure drop as the bag fills with dirt. This increase in pressure drop lowers the cleaning efficiency of the unit. It is for this reason that configurations for bagless vacuum cleaners are extremely appealing.
A bagless cleaning device is disclosed in WO 99/42198 based on PCT/GB99/00507 by the applicant herein. The full text of this publication is incorporated herein by reference. In this device, dirty inlet air is passed into the upper portion of a cyclone having a cylindrical cross-section and a lower frusto-conical section. This cyclone separation stage is designed to separate fine dirt particles in a collection chamber below the cone opening. The cylindrical portion of the device includes a transition zone connected to an adjacent side chamber for collection of coarse dirt particles. In another embodiment disclosed therein, coarse dirt is collected in an outer larger cylindrical chamber surrounding the inner frusto-conical cyclone separator.
Other bagless vacuum cleaner designs are shown in a series of related applications that issued to Royal Appliance Mfg. Co. based on an application that initially issued as U.S. Pat. No. 6,003,196 on Dec. 21, 1999. These patents disclose various types of upright vacuum cleaners including an air separation chamber that may be a cyclonic separation device. All the vacuum cleaners described in these patents include a filter disposed in the cyclonic air flow chamber or dirt cup upstream of the suction source.
U.S. Pat. No. 6,192,550 to Sanyo Electric Co. Ltd. also discloses a vacuum cleaning device having a rotatable filter disposed in a cyclonic air separation chamber. This device is particularly effective, because the rotatable feature of the filter allows removal of dirt entrained in the filter into the bottom of the dirt cup for easy disposal when the dirt cup is removed for cleaning. The contents of this patent are incorporated herein by reference.
While the use of cyclonic separators provides its own advantage, considerations related to the configuration of the vacuum cleaner as a whole may also affect the viability of the design. Motors used to power a fan to induce air flow tend to be the heaviest single component of the vacuum cleaner. The location of this weight may affect the ease with which the vacuum cleaner may be used. Where the weight of the motor is high relative to the rest of the components of the vacuum cleaner, the resultant high center of gravity for the vacuum may tend to make the assembly less stable for users. Thus, the ability to mount the motor low may offer additional stability and ease of use.
Mounting the motor below the separation chamber lowers the center of gravity of the vacuum cleaner that is important in a compact light weight design. The configuration affects design choices for the separation chamber. The use of a cyclonic separator requires that the chamber be substantially cylindrical, and of a sufficient diameter to allow for cyclonic air flow within. The separation chamber must be removable to allow it to be emptied, cleaned or replaced. Placement of the motor below the separation chamber may result in inefficient power to draw air entering the separation chamber at the top through the separation chamber.
Thus, while many of these bagless designs are improvements over conventional vacuums utilizing bag technology, it remains desirable to provide continued improvements and alternative designs to improve both the separation of dirt particles from air in the air separator chamber in a compact and light-weight design.